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    <title>gl_CullDistance - OpenGL 4 Reference Pages</title>
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    <div class="refentry" id="gl_CullDistance">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>gl_CullDistance — provides a mechanism for controlling user culling</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>Declaration</h2>
        <p>
            <code class="varname">gl_CullDistance</code> is a member of the
            <code class="varname">gl_PerVertex</code> named block:
        </p>
        <pre class="programlisting">    out gl_PerVertex {
        vec4 gl_Position;
        float gl_PointSize;
        float gl_ClipDistance[];
        float gl_CullDistance[];
    };</pre>
        <p>
        </p>
        <p>
            In fragment shaders, it is intrinsically declared as:
            <code class="fieldsynopsis"><span class="modifier">in </span><span class="type">float </span><span class="varname">gl_CullDistance[] </span>;</code>
        </p>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            The <code class="varname">gl_CullDistance</code> variable provides a
            mechanism for controlling user culling. The element
            <em class="parameter"><code>gl_CullDistance</code></em>[<span class="emphasis"><em>i</em></span>]
            specifies a cull distance for each plane <span class="emphasis"><em>i</em></span>.
            A distance of 0.0 means that the vertex is on the plane, a
            positive distance means that the vertex is inside the cull
            volume, and a negative distance means that the point is outside
            the cull volume. Primitives whose vertices all have a negative
            clip distance for plane <span class="emphasis"><em>i</em></span> will be
            discarded.
        </p>
        <p>
            The <code class="varname">gl_CullDistance</code> array is predeclared as
            unsized and must be sized by the shader either by redeclaring it
            with an size or by indexing it only with integral constant
            expressions. The size determines the number and set of enabled
            cull distances and can be at most
            <code class="varname">gl_MaxCullDistances</code>. The number of varying
            components consumed by <code class="varname">gl_CullDistance</code> will
            match the size of the array. Shaders writing
            <code class="varname">gl_CullDistance</code> must write all enabled
            distances, or culling results are undefined.
        </p>
        <p>
            As an output variable,
            <code class="varname">gl_CullDistance</code> provides the place for the
            shader to write these distances. As an input in all but the
            fragment language, it reads the values written in the previous
            shader stage. In the fragment language, the
            <code class="varname">gl_CullDistance</code> array contains linearly
            interpolated values for the vertex values written by a shader to
            the <code class="varname">gl_CullDistance</code> vertex output variable.
        </p>
        <p>
            It is a compile-time or link-time error for the set of shaders
            forming a program to have the sum of the sizes of the
            <code class="varname">gl_ClipDistance</code> and
            <code class="varname">gl_CullDistance</code> arrays to be larger than
            <code class="varname">gl_MaxCombinedClipAndCullDistances</code>.
        </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
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                <span class="bold"><strong>OpenGL Shading Language Version</strong></span>
            </th>
              </tr>
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                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Variable Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>1.10</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>1.20</strong></span>
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                <span class="bold"><strong>1.30</strong></span>
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                <span class="bold"><strong>1.40</strong></span>
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                <span class="bold"><strong>1.50</strong></span>
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                <span class="bold"><strong>3.30</strong></span>
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                <span class="bold"><strong>4.00</strong></span>
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                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.10</strong></span>
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                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.20</strong></span>
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                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.30</strong></span>
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                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.40</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.50</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">gl_CullDistance</td>
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                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
        <p>
            <a class="citerefentry" href="gl_ClipDistance.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_ClipDistance</span></span></a>,
            <a class="citerefentry" href="gl_PointSize.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_PointSize</span></span></a>
        </p>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 2014 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p>
      </div>
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